1. Field of the Invention
This invention pertains generally to systems for collecting solar energy for storage in the form of a heated fluid medium and particularly relates to solar energy systems having a plurality of reflecting surfaces for collecting and focusing solar radiation on a target.
2. Description of the Prior Art
It has been recognized by many that solar energy is a unique source of energy which for all practical purposes is constantly self-renewing, has no harmful side effects in its use, such as polution of the environment, etc. It is abundant in most of the inhabited portions of the world in sufficient amount to be utilized as an appropriate source of power during a major portion of the year. Many attempts have been made to exploit this "free" energy, particularly for use for home heating and other domestic hot water production. The many attempts have not met with outstanding success and all such systems generally rely on alternative sources of energy when sun light becomes unavailable due to weather condition or time of year. While such modern storage media as eutectic salts have been developed which show the capability of retaining heat concentrations of several hundred degrees for lengthy periods of time, the storage of enough heat energy at 150.degree. to last the average home through a month long cold cloudy period would require the dedication of more space in the home than most home owners are willing to allocate. The development of modern insulating materials are now making it possible to contain heat concentrations at even higher temperatures than before. The innovation of new storage media and superior insulating materials can be combined to provide a concentrated source of heat at high temperature thus providing increased reliability of the system.
In order that this heat level be obtained, it is necessary that the solar energy be concentrated by the use of appropriate optical devices together with heat collecting and transferring targets for transferring the solar energy collected to the heat storage media. Prior solar energy collectors have included trough-shaped refractors focusing the incident solar energy on a tube carrying a fluid media positioned at the focal point of the trough shaped reflector. The exposure of the media carrying tube over the length of the trough has the disadvantage, however, of permitting readmission of a significant portion of the heat collected by the media carrying tube. It has been therefore recognized that concentrating solar radiation might better be accomplished by the use of a parabolic reflector focusing the solar energy to a single point where an appropriate target is positioned. Several experimental parabolic reflectors have been constructed for the purpose of concentrating energy to achieve very high temperatures and some have recorded temperatures of several thousand degrees Fahrenheit. It is recognized that this much concentration is undesirable for domestic use but concentrations of several hundred degrees would be desirable. The construction of a single parabolic reflector capable of gathering sufficient energy to heat the average house would be undesirably large and present an extremely expensive investment prospect. An additional problem is posed by where to place such a structure since most home owners would be reluctant to sacrifice any significant portion of their property to such a structure and few homes could safely bear the weight of the necessary superstructure and control devices required for a single parabolic reflector having a reflecting surface of 400 to 600 square feet which would be needed to collect the necessary solar energy.